Medical Parasitology

By the end of the lecture, students are expected to be able to: Knows the history of Parasites Define the Parasitology Define the Medical Parasitology. Define the Parasites Define the host Define and describe the types of parasites Contrasts between the types of parasites Define and describe the types of Hosts Contrasts between the types of Hosts

History of Parasites parasitic disease have been with mankind since time immemorial. Even today. These diseases remain among the major causes of human misery and death in the world. The first discovery of parasite was recorded in eighteenth century and the discoveries have continued late into the twentieth century. The availability of microscope helped in discovery of new parasites.

Introduction to Parasitology Definitions Parasitology: Is the science which deals with parasites. Medical parasitology: is the science that deals with organisms living in the human body and the medical significance of this host-parasite relationship. Parasite: is a living organism which takes its nourishment and other needs from a host. Host: is an organism which supports the parasite.

Types of parasites 1- Ectoparasite: a parasitic organism that lives on the outer surface of its host, e.g. lice, ticks, mites.

2-Endoparasites: parasites that live inside the body of their host, e.g. Entamoeba histolytica.

3- Obligate Parasite: This parasite is completely dependent on the host during a part or all of its life cycle, e.g. Plasmodium spp.

4- Facultative parasite: an organism that exhibits both parasitic and non-parasitic modes of living. 5- Accidental parasite: is a parasite attacks an unnatural host and survives. E.g. Hymenolepis diminuta.

6- Erratic parasite: is one that wanders into an organ in which it is not usually found. E.g. Entamoeba histolytica in the liver or lung of humans.

The types of Hosts 1- Definitive host: Host that harbors a parasite in the adult stage or where the parasite undergoes sexual method of reproduction. 2- Intermediate host: Host that harbors the larval stages of the parasite or an asexual cycle of development takes place in the host. 3- Natural host: A host that is naturally infected with certain species of parasite.

4- Accidental host: A host that is under normal circumstances not infected with the parasite.